Mass spectrometer equipment for automatic gas analysis

ABSTRACT

Mass density signals furnished by a mass spectrometer, each signal corresponding to the mass density of particles with a particular mass number, are distributed to a number of circuit locations and stored. Upon occurrence of signals of a sufficient magnitude at selected ones of these locations a signal is generated by an AND circuit, which may start an alarm. The circuit locations are selected to correspond to mass density signals resulting from the presence of particles found in poison gas.

0 United States Patent [151 3,639,756 Schulz 1 Feb. 1, 1972 [54] MASS SPECTROMETER EQUIPMENT [56] References Cited FOR AUTOMATIC GAS ANALYSIS UNITED STATES PATENTS [72] inventor: Hansrichard Schulz, ViIlingen am Black 2,901,624 8/1959 Nier ..250/41.9 G F s ny v 3,005,911 10/1961 Burhans ..250/41.9 G [73] Assigneez Saba schwanwalder Apane Bau An 3,211,996 10/1965 Fox et a1. ..250/41.9 G

stalt August Schwer Sohne GrnblI, Villingen am m Forest, Germany Primary Exarnmer--Anthony L. Bush [22] Filed Jan 17 1969 Attorney-Michael S. Striker [21] App1.No.: 792,042 ABSTRACT Mass density signals furnished by a mass spectrometer, each [30] Foreign Appficamn priority Dam signal corresponding to the mass density of particles with a particular mass number, are distributed to a number of circuit .Ian. 20, 1968 Germany ..P I6 73 060.2 locations and Stored Upon occurrence of signals f a Suffi cient magnitude at selected ones of these locations a signal is [22] CC]! ..250/4l.9 G, 250l41.9 D generatcd by an AND circuit which may start an alarm The I A d circuit locations are selected to correspond to mass density o arc l E signals resulting from the presence of particles found in poison gas.

12 Claims, 8 Drawing Figures IDENTIFICATION MASS STAGE SPECTROMETER) AMPLIFIER COINCIDENCE MATRIX ACCELERATING SIGNAL GENERATOR MONITOR I l I TIMING FLY BACK AND SWITCHING SIGNAL GENERATOR GENERATOR PATENIEI] FEB H972 3.6391156 SHEET 1 OF 8 Fig.1

IDENTIFICATION MASS STAGE SPECTROMETER) AMPLIFIER COINCIDENCE MATRIX I r I ACCELERATING SIGNAL GENERATOR MONITOR I I TIMING FLY BACK AND GENERATOR SWITCHING SIGNAL GENERATOR Inventor: IMAM 20mm SUN 6 By M1 $1 PATENIEUFEB um 3.639.156

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rm; 12/: ma 0 9.41/62 MASS SPECTROMETER EQUIPMENT FOR AUTOMATIC GAS ANALYSIS BACKGROUND OF THE INVENTION This invention relates to a method and arrangement for the automatic analysis of gases by means of signals derived from a mass spectrometer. These mass spectrometer signals, or mass density signals are generated sequentially within a predetermined time period.

So far, equipment is only known for recording the signals generated by such a mass spectrometer. An automatic evaluation of these mass spectra, and particularly the automatic identification of certain gases as a function of the characteristic mass number of particles in said gas is not yet known.

SUMMARY OF THE INVENTION It is the object of this invention to furnish a method and arrangement for such an automatic identification. The basic idea of this invention consists in scanning the signals derived from a mass spectrometer and to generate a signal signifying the presence of a determined gas when signals signifying the presence of particles with a given mass number or a combination of such mass numbers which is characteristic for a particular gas appear.

The invention comprises a method for automatically generating an output signal in the presence of at least one selected gas within a gas mixture. It utilizes signals derived from a mass spectrometer, namely a plurality of mass density signals which appear in a determined time sequence during a determined time period. The signals are distributed to corresponding circuit locations and an output signal is generated when mass density signals appear at a circuit location signifying the presence ofa particular gas.

The output signal generated may be either an alarm signal or may be an indication showing the particular gas present.

For a more exact quantitative and qualitative analysis of the gas the mass density signals may be stored and may be compared by means of a data-processing arrangement with the characteristic mass density distribution for known gases, as for example poison gases. Under certain circumstances it may be sufficient to use one particular mass density signal, which corresponds to the typical mass number of the gas to be detected as an input to the data-processing arrangement.

It is further possible by use of this invention to monitor certain regions corresponding to a given range of mass numbers which are characteristic for a particular type of gas, as for example poison gases, automatically, and to generate an alarm signal in the presence ofsuch a gas.

It is possible with the arrangement and method in accordance with this invention to analyze the atmosphere in a given physical location completely automatically both qualita tively and quantitatively to determine the presence of dangerous gases both of known and unknown composition.

The completely electronic arrangement in accordance with this invention utilizes a mass spectrometer whose output is connected via an amplifier to a distributingmeans, as for example a matrix and from this matrix to the input of a plurality of demodulation stages. Either a single one of these demodulation stages, or a combination of these may serve as identification means to determine the presence of a given gas. The distributing means and the mass spectrometer are synchronized by means of synchronizing means which latter generate the required switching pulses for the distributing or coincidence matrix and further, generate the accelerating voltage for the mass spectrometer.

As a further extension of the present invention, a single identification stage may be furnished for monitoring a range of mass numbers. This particular identification stage may be directly controlled by the switching pulses and is connected with the output of the mass spectrometer via an amplifier. Since the mass density signals are furnished in timed sequence, as are the switching pulses, a selection of the particular switching pulses for energizing the identification stage corresponds to selection of a particular range of mass numbers.

If desired, an alarm may be generated in the presence of a signal of determined magnitude in this identification stage.

Use of this invention results in maximum security, since the air may be continuously monitored automatically. In order to insure proper operation of the equipment in accordance with a further extension of this invention it is possible to monitor mass density signals corresponding to normal air at regular intervals, and to indicate improper operation of the equipment in the absence of such characteristic mass density signals. A warning signal may then be generated in such absence to indicate improper equipment operation. It is further possible to generate a control signal for automatic adjustment of the equipment if deviations from the normal values occur.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a block diagram of the arrangement in accordance with this invention;

FIG. 2 is a circuit diagram of the accelerating voltage generator (3) of FIG. 1;

FIG. 3 is the mass spectrum of a dangerous gas, including the switching pulse scale beneath the abscissa;

FIGS. 4a and 4b shown the circuit diagram of the synchronizing means;

FIG. 5 is a section of the coincidence matrix 6 in FIG. 1;

FIG. 6 is the circuit diagram of an identification stage using three characteristic mass numbers; and 7 FIG. 7 is a monitoring arrangement (8, FIG. 1) for monitoring a range of mass numbers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be explained with referencetothe figures. The block diagram of FIG. I shows the arrangement of the equipment in accordance with this invention, while FIGS. 2 to 7 show the possible circuit embodiments of the different blocks as illustrated in FIG. 1.

Block I in FIG. 1 denotes a timing generator which furnishes the basic timing signals used in synchronizing the accelerating signal of voltage for the mass spectrometer and the switching signals used in the distributing means 6, which may be a coincidence matrix. The timing signal generator 1, as well as the switching pulse generator and fly-back pulse generator 2 together constitute the synchronizing means. The accele rating signal for accelerating the ions in the mass spectrometer are furnished by accelerating signal generator means 3. The accelerating signals derived therefrom are applied to the mass spectrometer 4. The mass density signals generated by said mass spectrometer asa function of said accelerating signal are amplified in an amplifier 5 and distributed by distributing means 6 which may as previously stated be a matrix. The output of the matrix is connected to a plurality of circuit locations, one or more of which is shown here as identification stage 7. The mass density signals from the mass spectrometer, after being amplified in amplifier 5 may also be applied to monitoring means, 8, which are directly controlled by switching signals generated in stage 2. The monitoring means may be used to monitor a determined range of mass numbers under direct control of the switching signals. Thus it may be used to monitor the air for poison gases whose exact composition is not known but whose characteristic mass numbers are known to lie within a determined range.

The synchronization between the accelerating signal for th mass spectrometer and the switching signals must of course be very strict for proper operation of the system, since the mass density signal generated by the mass spectrometer corresponds to a different mass number for each value of accelerating voltage, and it is of course essential that the mass density signal corresponding to the correct mass number be furnished to the corresponding circuit location under the control of the switching signals. Thus a varying accelerating voltage is applied to the mass spectrometer, while in synchronism thereto, switching signals are generated which connect the output of the distributing means sequentially to different circuit locations, as will be discussed in more detail below.

FIG. 2 shows a circuit diagram of the accelerating voltage generator 3 in FIG. 1. Switching pulse generator 2 also generates fly-back signals or pulses. These fly-back pulses are applied to the base of a transistor by means of a threshold diode 9. A condenser 12 connected to the emitter of transistor 10 via a diode 11 is charged to its maximum voltage by means of the applied fly-back pulses. The transistor 10 and its associated components comprise means for charging the capacitor means, namely capacitor 12. The capacitor discharges via discharge means, namely the resistors 13a through 13d, since, when no fly-back pulse is being applied, the transistor 10 is blocked, as is silicon diode 11. The voltage across the capacitor thus decreases exponentially during the time no fly-back pulse is being applied.

A cathode follower stage comprising the two transistors 14a and 14b uses this exponentially decreasing voltage and applies it to a DC amplifier which is not shown and which amplifies it to the value required for the accelerating voltage for the spectrometer. The stability of this voltage is assured by a stabilized supply voltage and high-quality components. This exponentially decreasing voltage causes an exponential increase in the mass number series, since the mass number is inversely proportional to the accelerating voltage. For a linear sequence of switching pulses with respect to time the higher mass numbers are compressed, that is a logarithmic relationship exists between the mass number scale and the time scale, or switching signal scale.

Of course, the accelerating voltage may have a different shape rather than the exponential shape discussed above. For example a hyperbolic accelerating voltage would result in a linear mass number scale. However, as shown with the aid of equations 2 and 4 below, the exponential shape for the accelerating voltage is preferable.

A typical mass spectrum for a poison gas is shown as an example in FIG. 3. Mass numbers in the range m to m (for example "1 m=l 30) are shown along the abscissa, while the ordinates show the mass density. A further scale parallel to the abscissa shows the time sequence of the switching pulses from =l to n=N (for example N=224). This shows the relationship between the mass numbers and the switching signals or pulses. Thus the first switching pulse (n=l) in this example corresponds to the mass number m while the last switching pulse (n=N corresponds to the mass number m For an exponentially decreasing accelerating voltage the following relationship exists between the mass number m and the switching pulse number n:

Since of course only whole numbers may be used as switching pulse numbers, the number n resulting from the above formula 2 must be rounded off to the nearest whole or integral number.

FIGS. 4a and 4b jointly show the circuit arrangement for the synchronizing means, and thus corresponds to blocks 1 and 2 in FIG. I. Mainly, these circuits consist of first matrix means for generating the first group of switching signals, lettered r to r in FIG. 4a and second matrix means for generating the second group of switching signals denoted by s, to s in FIG. 4b. The first matrix means in FIG. 4a are controlled by a plurality of first frequency divider means labeled 18a through 18d in FIG. 4a. These frequency divider means may be. for example, four flip-flop stages; the second matrix means are similarly controlled by means of a plurality ofsecond frequency divider means, labeled stages 19a through 19d in FIG. 4!). Stages through 19d may also be flip-flops. This two matrix arrangement differs from the conventional single matrix which in this case would have to be controlled by eight binary (flip-flop) stages and would require 8-2==2,048 matrix elements (diode) for generating 256 switching signals or pulses. As shown in FIGS. 4a and 4b, two similar matrices, each controlled by four binary states, are shown. The inputs of the coincidence matrix shown in FIG. 5 are then connected to one output each of the first and second matrices (R and S matrix respectively), thus causing the outputs of the coincidence matrix to be energized in a time-sequential order.

The number of diodes required for the two matrices R and S are:

The coincidence matrix for an output of 256 switching pulses requires at the most 2256=5 l2 diodes. Thus a total of 640 diodes is required. The saving in diodes in this example for eight binary stages and 256 switching signal outputs is 1,408 diodes.

In FIG. 4a the timing signal generator means are shown as a timing oscillator means 15 which may be a quartz oscillator which generates a stable sinusoidal oscillation, as well as a Schmitt trigger, 16, which shapes the sinusoidal oscillations into square pulses with sufficiently short rise and fall times. These rectangular pulses are applied to flip-flop 17 which serves as a frequency divider. Flip-flop 17 in turn furnishes pulses in the form of symmetrical square pulses of short rise and fall times to the serially connected frequency divider means or binary stages 18a, 18b, 18c, 18a in FIG. 4a and 19A, 19b, 19c, and 19d in FIG. 4b. From the square pulses generated in the first four binary stages 18a, 18b, 18c and 18d a regularly times sequential sequences of R switching pulses r to r is derived by means ofR" matrix 20. In the same way the 5" matrix 21 under control of the corresponding four binary stages l9a, 19b, 19c, and 19d generate a regular sequence of l6 S" switching pulses s, to s However, the duration ofswitching pulses r, to s is each 16 times the duration of the corresponding R" switching pulse. By combining one each of the R" switching pulses and of the 8" switching pulses 16X 1 6 256 coincidence switching pulses appear in a regular time sequence which repeats cyclically. The duration of each coincidence switching pulse of course corresponds to the duration ofthe R switching pulse.

Reference to FIG. 4b further shows a flip-flop 22 which is used for generation of the fly-back pulses. Reference to the figure shows that flip-flop 22 is controlled by a gate 23a and a second gate 23b. Thus the flip-flop is set to a first position in response to the coincident presence of switching pulse r and switching pulse s while its second position is controlled by coincidence of switching pulses r and s,,,. Since the combination of r and s corresponds to the 225th coincidence switching pulse and r s corresponds to the 256th coincidence switching pulse (or coincidence matrix output) the duration of the fly-back pulse is from said 255th to said 25 6th coincidence switching pulse. Upon occurrence of the 256th switching pulse the binary stages 18 and 19 are reset via line 230.

FIG. 5 shows a section of the distributing means, or coincidence matrix 6. It is the function of this matrix to distribute the mass density signals from the mass spectrometer 4 after amplification in amplifier 5, by use of the switching signals derived from the R and S matrices to the different circuit locations, or inputs to the identification stages.

As discussed in relationship with FIG. 3 in detail, a 1:1 relationship in time exists between the mass numbers of the mass density signals and the switching pulses. In this manner a present" mass number is indicated by the appearance of mass density signal of a value other than 0. The time range in which this mass density signal can appear must coincide with the time range in which the switching pulse or signal corresponding to this mass number appears, so that the coincidence matrix causes the mass density signal in this time range to be applied to the corresponding circuit location, which is the selected output of the coincidence matrix or, equivalently an input to one of the identification stages.

The amplified mass density signals, whose zero level must of course be kept constant, are applied to the matrix 6, as illustrated in FIG. 5, over conductor 24. If, for example, the mass density signal corresponds to the smallest mass number of the range of mass numbers which is being scanned automatically, it will coincide in time with the first switching pulse, I,, which is formed in the coincidence matrix from input switching pulses r, and r,. The mass density signal is thus switched through to output 1,. The voltage of the mass density signal on line 24 must always be smaller than that of the switching pulses, in order that any limiting of the mass density signal is avoided. In this way the signals appearing at J, through J are always proportional in amplitude to the amplitude of the mass density signals. Thus the coincidence matrix shown in FIG. 5 causes a signal to appear at one of the outputs J, to J when a mass density signal which differs from coincides in time with the corresponding switching pulses devised from the R and switching pulses. If, for example the mass density signal mentioned above, namely that corresponding to the smallest mass number, does not appear, no signal appears at output J,, despite the appearance of switching pulses r, and s,, since the diode connecting the line 24 to the output J, causes this output to be clamped to 0.

Reference to FIG. 5 and the section of the coincidence matrix shown therein shows in which way any of the outputs J J J may be selected by means of the appropriate combinations of the first group of switching signals or pulses r, through r,,, and the second group of switching signals or pulses 5,, s s Thus, of the 256 possible switching pulse combinations. 224 are used for the actual scanning of the mass spectrum, while the remaining 32 pulses, namely pulses 225 to 256 are assigned to the time required for the fly-back of the accelerating potential of the mass spectrometer. In this fly-back time the ion-accelerating potential is returned to its initial value. Furthermore, the 256 pulse is used to reset all the binary stages to their initial condition, thus causing the same correspondence between mass number and switching pulses to reoccur during the next scanning period.

FIG. 6 shows a typical identification stage, denoted by stage 7 in FIG. I. In this particular case the output signal is to occur for the simultaneous appearance of the three mass numbers m,, m. and m This figure will be used to explain the operation of one such identification stage with respect to the way in which the output signal, in this case an alarm signal, is generated and how a further signal is derived for quantitative indication of the gas present.

Mass density signals corresponding to mass numbers m,, m and m are applied to the identification stage at input 25, 26 and 27 which are connected to three outputs of the coincidence matrix 6. The mass density signals are separately amplified in cathode follower stages 28, 29 and 30 and demodulated by means of diodes, The DC voltages derived from the three demodulation diodes are applied to capacitors 31, 32 and 33 respectively and are stored there for a plurality of scanning periods. The time constant of these demodulation stages should correspond to at least 4 scanning periods, that is,

it should extend over 1,000 scanning outputs for the abovediscussed situation of 256 pulses per scanning period. In this case the fact that the signals are generated by sequential scanning makes no difference in the derived DC voltages which now exist simultaneously and thus can be used for a coincidence indication. Thus the three demodulating stages are connected together in such a manner that a positive voltage appears at the joint output of the diodes only when all three mass density signals appeared. That is, these three demodulation stages are actually connected together in an AND circuit. Thus if all three mass density signals m,, m and m, appear, the positive voltage appearing at the joint output is amplified by DC amplifier comprising transistors 37a, 37b and 376, at the output 38 of which a positive voltage will then appear. This voltage may be used to activate an alarm signal and may also be used to initate a qualitative indicator. This DC voltage further furnishes the operating voltage for amplifier 39 which causes a typical mass density signal, in this case the signal corresponding to mass number m,,, to be applied to a data-processing arrangement via the terminal 390. For purposes of clarity neither the alarm system nor the dataprocessing unit is shown here.

FIG. 7 of the drawing shows a circuit for monitoring a determined region of mass numbers, as indicated in block diagram form, block 8, of FIG. 1. In this circuit gates 40 and 41 each have two inputs for receiving one R and one S switching pulse each for controlling the state of flip-flop 42. This flipflop one embodiment of gating means is used to generate a positive voltage during the whole time corresponding to the mass number region to be monitored. Thus a monitoring signal is generated which coincides with any mass density signal applied at input 44 which is contained within the mass number regions to be monitored. These mass numbers will be chosen to be in a region which indicates the presence of, for example, a poison gas. In case of such a coincidence the resulting signal is amplified by the stages associated with transistors 52a, 52b and 52c amplifier and may cause an alarm signal to be generated as well as furnishing a signal for quantitative analysis, if desired. Of course, if mass numbers are contained within the region which may be present in normal air, it will be desirable to suppress the alarm output for such signals. This is accomplished by transistor 45 which serves to connect the monitoring signal to ground thus constituting means for short circuiting the input of said amplifier means when mass numbers corresponding to particles normally found in air are being scanned. The switch is controlled via gates 46, 47 and 48 and diodes 49, 50 and 51 associated with each of said gates. Appropriate "R" and S switching signals applied to the input of gates 46, 47 and 48 cause transistor 45 to short-circuqt whenever the mass density signal appearing at input 44 corresponds to a mass number normally associated with air. Thus no alarm is generated for mass density signals corresponding to those of normal air.

A further consideration in constructing an embodiment of the present invention is that the number N of coincidence matrix outputs, or of coincidence switching signals, must be greater than the total number 2 of definable mass numbers determined by the resolution a==m/Am of the mass spectrometer and by the chosen mass number region m m n Under these conditions a plurality of coincidence switching pulses coincide with the mass density signal for each mass number so that the particular coincidence matrix output at which the maximum signal occurs may be chosen as an input for the corresponding identification stage.

The number Z of individually recognizable mass numbers may be derived with the aid of the following geomelr i c s eries:

This leads to:

Comparing equation (4) with equation (2) shows the same logarithmic dependence of the number 2 and the switching pulse number n to the mass number. Thus it may be concluded that the exponentially decreasing accelerating voltage in accordance with this invention causes a lzl relationship between the coincidence switching pulse and the identifiable mass number at each location of the scanned mass number regions. If for example at the lower edge of the scanned mass number region three coincidence switching pulses are received for one mass density signal, then all other locations in this region also receive three coincidence switching pulses for the mass density signals generated thereon. For N to be greater than Z the following inequality must then hold:

If for example the mass number region from m =3O to m 130 is to be scanned and the resolution a of the mass spectrometer is a=m/Am =l00, then the number Z of separately identifiable mass numbers may be calculated according to Formula (4) as follows:

Z=1+ In 1.01

The number N =224 of coincidence switching pulses mentioned in the example given above would thus satisfy the inequality relationship of equation (5) with a minimum of components.

The equipment may have built-in error detection as follows. A special identification stage having inputs corresponding to mass numbers normally present in air may be switched periodically and may generate a signal signifying that the equipment is in proper operation to a central control location.

In case of improper operation of the equipment the characteristic mass density signals will not arrive in proper time sequence so that no coincidence is possible. In this case a failure signal may be transmitted to the central control locat1on.

The equipment requires a stabilized supply which should preferably be combined with a floating storage battery in order to assure proper circuit operation even in the case of supply voltage failure.

Furthermore a flip-flop may be triggered from the timing pulse generator via appropriate gates. This may be used to derive a synchronization signal from the timing pulses during the fly-back time thus permitting a synchronization for remote transmission which is analogous to color television transmission. In this way remotely derived mass density signals may be evaluated in a central station.

While the invention has been illustrated and described as embodied in a particular type of analyzer arrangement, it is not intended to be limited to the details shown, since various modifications and circuit changes may be made without departing in any way from the spirit of the present invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. An arrangement for automatically generating an output signal signifying the presence of at least one selected gas within a gas mixture, each gas within said gas mixture having particles of at least one corresponding mass number, comprising, in combination: mass spectrometer means for generating mass density signals sequentially in time in response to an accelerating signal, each of said mass density signals corresponding to the mass density of a given particle within said gas mixture; accelerating signal generating means for furnishing said accelerating signal; distributing means comprising coincidence matrix means, for distributing at least selected ones of said mass density signals, each to a corresponding one of a plurality of circuit locations in response to switching signals; identification means for generating said output signal in response to mass density signals at selected ones of said corresponding circuit locations; and synchronizing means for synchronizing said accelerating signal generator means and said distributing means, said synchronizing means comprising timing oscillator means; a plurality of first frequency divider means, connected to said timing oscillator means and interconnected in series; first matrix means connected to said plurality of first frequency divider means for combining the outputs of said plurality of first frequency divider means in such a manner that a first group of switching signals is generated; a plurality of second frequency divider means, series-interconnected and connected in series to said plurality of first frequency divider means; second matrix means for combining the outputs of said plurality of second frequency divider means in such a manner that a second group of switching signals is generated, said coincidence matrix means being responsive to substantially simultaneous reception of one of said first and one of said second group of switching signals.

2. An arrangement as set forth in claim 1 wherein said identification means comprise demodulating means for demodulating said mass density signals, and storage means for storing each demodulated mass density signal, thus generating stored mass density signals.

3. An arrangement as set forth in claim 2 wherein each of said identification means further comprises logic means for generating said output signal in the simultaneous presence of stored mass density signals at selected circuit locations.

4. An arrangement as set forth in claim 3 wherein said logic means comprise an AND circuit.

5. An arrangement as set forth in claim 2, further comprising means for applying said output signal to a date-processing arrangement for quantitative evaluation.

6. An arrangement as set forth in claim 1 wherein said accelerating signal generator means comprise capacitor means; means for charging said capacitor means in response to a selected one of said first group and a selected one of said second group of switching signals; and discharge means associated with said capacitor means for permitting the discharge thereof, said accelerating signal corresponding to the voltage across said capacitor during the discharge thereof.

7. An arrangement as set forth in claim 6 further comprising a cathode follower stage for coupling said accelerating signal generator means to said mass spectrometer means.

8. An arrangement as set forth in claim 6, wherein the mass number m corresponding to each of said mass density signals which are related to the number of the switching signal in accordance with the following formula:

where m=l is the first switching signal in the time interval defined by said capacitor discharge; m is the mass number associated with the mass density signal switched by said first switching signal; N is the last switching signal within the time interval defined by said capacitor means discharge; and m is the mass number of the mass density signals switched by said last switching signal.

9. An arrangement as set forth in claim 8 wherein the switching signal number n corresponding to a given mass number m is equal to:

11. An arrangement as set forth in claim 1 also comprising Schmitt trigger means for shaping the output of said timing oscillator means.

12. In a gas detection arrangement for detecting the presence of a determined gas in air, in combination. means for furnishing mass density signals indicative of the presence of said gas and further mass density signals indicative of the presence of air; and identification means responsive to said further mass density signals for generating a failure signal indicative of incorrect operation of said arrangement in the absence of said further mass density signals. 

1. An arrangement for automatically generating an output signal signifying the presence of at least one selected gas within a gas mixture, each gas within said gas mixture having particles of at least one corresponding mass number, comprising, in combination: mass spectrometer means for generating mass density signals sequentially in time in response to an accelerating signal, each of said mass density signals corresponding to the mass density of a given particle within said gas mixture; accelerating signal generating means for furnishing said accelerating signal; distributing means comprising coincidence matrix means, for distributing at least selected ones of said mass density signals, each to a corresponding one of a plurality of circuit locations in response to switching signals; identification means for generating said output signal in response to mass density signals at selected ones of said corresponding circuit locations; and synchronizing means for synchronizing said accelerating signal generator means and said distributing means, said synchronizing means comprising timing oscillator means; a plurality of first frequency divider means, connected to said timing oscillator means and interconnected in series; first matrix means connected to said plurality of first frequency divider means for combining the outputs of said plurality of first frequency divider means in such a manner that a first group of switching signals is generated; a plurality of second frequency divider means, seriesinterconnected and connected in series to said plurality of first frequency divider means; second matrix means for combining the outputs of said plurality of second frequency divider means in such a manner that a second group of switching signals is generated, said coincidence matrix means being responsive to substantially simultaneous reception of one of said first and one of said second group of switching signals.
 2. An arrangement as set forth in claim 1 wherein said identification means comprise demodulating means for demodulating said mass density signals, and storage means for storing each demodulated mass density signal, thus generating stored mass density signals.
 3. An arrangement as set forth in claim 2 wherein each of said identification means further comprises logic means for generating said output signal in the simultaneous presence of stored mass density signals at selected circuit locations.
 4. An arrangement as set forth in claim 3 wherein said logic means comprise an AND circuit.
 5. An arrangement as set forth in claim 2, further comprising means for applying said output signal to a date-processing arrangement for quantitative evaluation.
 6. An arrangement as set forth in claim 1 wherein said accelerating signal generator means comprise capacitor means; means for charging said capacitor means in response to a selected one of said first group and a selected one of said second group of switching signals; and discharge means associated with said capacitor means for permitting the discharge thereof, said accelerating signal corresponding to the voltage across said capacitor during the discharge thereof.
 7. An arrangement as set forth in claim 6 further comprising a cathode follower stage for coupling said accelerating signal generator means to said mass spectrometer means.
 8. An arrangement as set forth in claim 6, wherein the mass number m corresponding to each of said mass density signals which are related to the number of the switching signal in accordance with the following formula: where m 1 is the first switching signal in the time interval defined by said capacitor discharge; m1 is the mass number associated with the mass density signal switched by said first switching signal; N is the last switching signal within the time interval defined by said capacitor means discharge; and m2 is the mass number of the mass density signals switched by said last switching signal.
 9. An arrangement as set forth in claim 8 wherein the switching signal number n corresponding to a given mass number m is equal to: where m1 is the mass number associated with the mass density signal switched by N, first switching signal; N is the last switching signal Z the time interval defined by said capacitor means discharge; and m2 is the mass number of m/ Delta switching N>
 10. An arrangement as set forth in claim 9 wherein the total number of switching signals, N, for each capacitor discharge period, exceeds the number Z of distinguishable mass numbers within the mass number region as determined by the resolution of said mass spectrometer means, m/ Delta m, or N> Z
 11. An arrangement as set forth in claim 1 also comprising Schmitt trigger means for shaping the output of said timing oscillator means.
 12. In a gas detection arrangement for detecting the presence of a determined gas in air, in combination, means for furnishing mass density signals indicative of the presence of said gas and further mass density signals indicative of the presence of air; and identification means responsive to said further mass density signals for generating a failure signal indicative of incorrect operation of said arrangement, in the absence of said further mass density signals. 